In these stands, there is a need to facilitate initial and final positioning operations, enabling the legs to be extended quickly and simultaneously or, conversely, to be returned rapidly from the extended position to a fully retracted position.
For this purpose, it is known to provide controls which enable the locking systems of the three legs to be controlled simultaneously. An example of this technology is described in U.S. Pat. No. 4,666,112. This document provides for each tripod leg to comprise only two elements which are slidable telescopically relative to one another; with the three locking means operated simultaneously by a single common sleeve control associated with a central pillar and connected to the legs by means of the three arms of a spreader. A disadvantage of this device is that the spreader imposes a specific and predetermined relative positioning of the legs, limiting the versatility of use of the tripod. It also controls only one telescopic extension for each leg.
The simultaneous control of two or more extensions of a particular tripod leg is also known from U.S. Pat. No. 5,887,835.
However, this technical solution enables the three legs to be controlled simultaneously only by a complex manoeuvre to operate all of the locking devices on the legs at the same time.